1. Field of the Invention
The present invention relates to a control device for an internal combustion engine having a cylinder resting mechanism, and particularly, to a device for determining an intake/exhaust valve operation state.
2. Description of the Background Art
In recent years, problems of environmental conservation and fuel depletion have been raised, and it is a great challenge to address these problems also for automobile industry. In addressing these problems, an internal combustion engine is developed which has a cylinder resting mechanism configured to rest fuel injection and valve driving in some of a plurality of cylinders and perform operation with the other cylinders.
Conventionally, as a device for determining a valve operation state of an internal combustion engine having a cylinder resting mechanism, a device for determining a valve operation state, depending on whether or not intake pulsation due to an intake process of each cylinder occurs, based on output of an air flow meter, is proposed (for example, see Japanese Laid-Open Patent Publication No. 2009-270492, hereinafter, Patent Document 1), and a device for determining a valve operation state based on an exhaust air fuel ratio is proposed (for example, see Japanese Laid-Open Patent Publication No. 2012-92745, hereinafter, Patent Document 2).
In an internal combustion engine having a cylinder resting mechanism, while the operation state of one valve is normal, the operation state of the other valve may be abnormal. In the conventional device shown in Patent Document 1, since the valve operation state is determined based on output of an air flow meter provided on the intake side, the operation state of an exhaust valve cannot be determined when an intake valve is closed. On the other hand, in the conventional device shown in Patent Document 2, since the valve operation state is determined based on output of an exhaust air fuel ratio sensor provided on the exhaust side, the operation state of an intake valve cannot be determined when an exhaust valve is closed.